Simple Auditory Discrimination Research Articles

Cognitive load exacerbates rightward biases during computer maze navigation

Neurologically healthy individuals exhibit subtle attentional asymmetries, such that attention is preferentially directed leftwards for objects in near space and rightwards for objects in far space. These attentional biases also affect navigation and cause people to deviate to the right when passing through an aperture. The current study examined whether the rightward deviations observed in real-world environments translate to simulated environments. As proof of concept and to determine whether rightward biases could be further exacerbated, the degree of cognitive load imposed on participants was manipulated. Experiment 1 asked participants to navigate through the centre of a computer-based doorway. In one block of trials, participants completed the task by itself (baseline condition), while in another block of trials they also completed a simple auditory discrimination task (load condition). While analyses revealed rightward biases for both conditions, the difference between conditions was not significant. Experiment 2 therefore increased the difficulty of the auditory task. Analyses revealed a significant difference between conditions, suggesting that the degree of cognitive load further exacerbates rightward biases, demonstrating that the rightward asymmetries in navigation observed in the real world generalises to a simulated environment and that this phenomenon behaves in a way that is consistent with pseudoneglect.

What happens to an individual visual working memory representation when it is interrupted?

This study tested the hypothesis that even the simplest cognitive tasks require the storage of information in working memory (WM), distorting any information that was previously stored in WM. Experiment 1 tested this hypothesis by requiring observers to perform a simple letter discrimination task while they were holding a single orientation in WM. We predicted that performing the task on the interposed letter stimulus would cause the orientation memory to become less precise and more categorical compared to when the letter was absent or when it was present but could be ignored. This prediction was confirmed. Experiment 2 tested the modality specificity of this effect by replacing the visual letter discrimination task with an auditory pitch discrimination task. Unlike the interposed visual stimulus, the interposed auditory stimulus produced little or no disruption of WM, consistent with the use of modality-specific representations. Thus, performing a simple visual discrimination task, but not a simple auditory discrimination task, distorts information about a single feature being maintained in visual WM. We suggest that the interposed task eliminates information stored within the focus of attention, leaving behind a WM representation outside the focus of attention that is relatively imprecise and categorical.

The Magnetic Acoustic Change Complex and Mismatch Field: A Comparison of Neurophysiological Measures of Auditory Discrimination

The Acoustic Change Complex (ACC), a P1-N1-P2-like event-related response to changes in a continuous sound, has been suggested as a reliable, objective, and efficient test of auditory discrimination. We used magnetoencephalography to compare the magnetic ACC (mACC) to the more widely used mismatch field (MMF). Brain responses of 14 adults were recorded during mACC and MMF paradigms involving the same pitch and vowel changes in a synthetic vowel sound. Analyses of peak amplitudes revealed a significant interaction between stimulus and paradigm: for the MMF, the response was greater for vowel changes than for pitch changes, whereas, for the mACC, the pattern was reversed. A similar interaction was observed for the signal to noise ratio and single-trial analysis of individual participants’ responses showed that the MMF to Pitch changes was elicited less consistently than the other three responses. Results support the view that the ACC/mACC is a robust and efficient measure of simple auditory discrimination, particularly when researchers or clinicians are interested in the responses of individual listeners. However, the differential sensitivity of the two paradigms to the same acoustic changes indicates that the mACC and MMF are indices of different aspects of auditory processing and should, therefore, be seen as complementary rather than competing neurophysiological measures.

Effect of exercise on the auditory discrimination task in perimenopausal women: a preliminary study

Background The climacteric phase of menopausal transition (perimenopause) is marked by reproductive hormone fluctuations and reduced cognitive capacity. Exercise enhances neurocognitive performance. However, auditory perceptual sensitivity has not been examined.Purpose This study aimed to determine the effect of aerobic exercise on the response speed (reaction time) and error rate during auditory processing among perimenopausal women.Methods Three pitches (500, 1000, and 2000 Hz) were used during a simple auditory discrimination task, which was performed before and after exercise. We included 14 perimenopausal women and 17 right-handed young women (aged 46–54 years and 18–22 years, respectively). To achieve similar exercise intensity in both groups, we proposed two types of physical activities for each group. Mixed models statistics were used to analyze the reaction time and error rate before and after training in the two groups.Results Perimenopausal women exhibited a significantly longer reaction time than young women during the baseline auditory discrimination task (p < 0.05) but not during the second test. The error rate decreased significantly after exercise among perimenopausal women (p < 0.05) but not among young women. Thus, exercise had a stronger beneficial influence on auditory plasticity or sensitivity for perimenopausal women than for young women.Conclusion The ability of aerobic exercise to modulate auditory neurocognitive performance differs between the two groups. Aerobic exercise improves auditory discrimination performance specifically for perimenopausal women. These results provide preliminary evidence concerning the acoustic features of middle-aged women, underscoring the importance of exercise for preventing decline in auditory cognitive function in perimenopausal women.

Emergent selectivity for task-relevant stimuli in higher-order auditory cortex.

A variety of attention-related effects have been demonstrated in primary auditory cortex (A1). However, an understanding of the functional role of higher auditory cortical areas in guiding attention to acoustic stimuli has been elusive. We recorded from neurons in two tonotopic cortical belt areas in the dorsal posterior ectosylvian gyrus (dPEG) of ferrets trained on a simple auditory discrimination task. Neurons in dPEG showed similar basic auditory tuning properties to A1, but during behavior we observed marked differences between these areas. In the belt areas, changes in neuronal firing rate and response dynamics greatly enhanced responses to target stimuli relative to distractors, allowing for greater attentional selection during active listening. Consistent with existing anatomical evidence, the pattern of sensory tuning and behavioral modulation in auditory belt cortex links the spectrotemporal representation of the whole acoustic scene in A1 to a more abstracted representation of task-relevant stimuli observed in frontal cortex.

Cross-Modal Phase Reset Predicts Auditory Task Performance in Humans

In the multisensory environment, inputs to each sensory modality are rarely independent. Sounds often follow a visible action or event. Here we present behaviorally relevant evidence from the human EEG that visual input prepares the auditory system for subsequent auditory processing by resetting the phase of neuronal oscillatory activity in auditory cortex. Subjects performed a simple auditory frequency discrimination task using paired but asynchronous auditory and visual stimuli. Auditory cortex activity was modeled from the scalp-recorded EEG using spatiotemporal dipole source analysis. Phase resetting activity was assessed using time-frequency analysis of the source waveforms. Significant cross-modal phase resetting was observed in auditory cortex at low alpha frequencies (8-10 Hz) peaking 80 ms after auditory onset, at high alpha frequencies (10-12 Hz) peaking at 88 ms, and at high theta frequencies (∼ 7 Hz) peaking at 156 ms. Importantly, significant effects were only evident when visual input preceded auditory by between 30 and 75 ms. Behaviorally, cross-modal phase resetting accounted for 18% of the variability in response speed in the auditory task, with stronger resetting overall leading to significantly faster responses. A direct link was thus shown between visual-induced modulations of auditory cortex activity and performance in an auditory task. The results are consistent with a model in which the efficiency of auditory processing is improved when natural associations between visual and auditory inputs allow one input to reliably predict the next.

Visual modulation of auditory cortical activity correlates with behaviour

Event Abstract Back to Event Visual modulation of auditory cortical activity correlates with behaviour Jeremy D Thorne1*, Maarten De Vos1, Filipa C. Viola1 and Stefan Debener1 1 University of Oldenburg, Germany Behavioural responses to auditory stimuli are facilitated by visual input even when visual stimuli are task irrelevant. In a recent study, we showed that a significant proportion of the variance in such behavioural response times was accounted for by the degree of visually-induced phase reorganisation of oscillatory activity in auditory cortex (Thorne et al., 2011). These results may in part have related to the widespread entrainment of cortical responses, evident in the EEG, to the rhythmic stimulus presentation used. Here we investigated electrophysiological correlates of audiovisual (AV) interactions using simple, isolated AV stimuli. Twenty healthy adults performed a simple auditory discrimination task using both auditory and AV stimuli. Visual-auditory stimulus onset asynchrony (SOA) was varied between 0 and 100 ms. Analysis of behavioural responses showed that with short SOAs (< 50 ms), responses to AV stimuli were slower than to auditory stimuli alone, while with long SOAs, responses to AV stimuli were faster. A comparison of auditory evoked potentials with the equivalent waveforms derived from AV data revealed that the amplitude of the N1 peak was increased by visual input with short SOAs (< 50 ms) but was attenuated by visual input with longer SOAs. Although the role of cross-modal phase resetting in the present data is as yet unclear, the electrophysiological results were thus remarkably consistent with the behavioural results. We conclude that these data provide further evidence that the efficiency of auditory processing is improved when auditory onset can be predicted by visual input. Keywords: Perception, SOA Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neurophysiology of Sensation and Perception Citation: D Thorne J, De Vos M, Viola FC and Debener S (2011). Visual modulation of auditory cortical activity correlates with behaviour. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00357 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Jeremy D Thorne, University of Oldenburg, Oldenburg, Germany, jeremy.thorne@uni-oldenburg.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Jeremy D Thorne Maarten De Vos Filipa C Viola Stefan Debener Google Jeremy D Thorne Maarten De Vos Filipa C Viola Stefan Debener Google Scholar Jeremy D Thorne Maarten De Vos Filipa C Viola Stefan Debener PubMed Jeremy D Thorne Maarten De Vos Filipa C Viola Stefan Debener Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Event-related potential and autonomic signs of maladaptive information processing during an auditory oddball task in panic disorder

Various empirical data suggest that individuals with Panic Disorder (PD) fail to appropriately assign significance to sensory stimuli within the internal and external milieu, including those stimuli which are patently threat-neutral. The failure to appropriately discriminate ‘signal’ stimuli from among ‘noise’ signals [Gordon, E., Liddell, B.J., Brown, K.J., Bryant, R., Clark, C.R., Das, P., et al. 2007. Integrating objective gene–brain-behavior markers of psychiatric disorders. J. Integr. Neurosci. 6, 1–34.] results in disturbances of information processing and attentional deployment, which manifests across multiple levels of functioning (e.g., brain, behaviour, autonomic). The present event-related potential (ERP) study, therefore, investigated attentive information processing in PD, using a standard two-tone auditory oddball paradigm, to assess patients' response to infrequent ‘target’ tones (i.e., signals) and frequent ‘non-target’ tones (i.e., noise). Simultaneously-recorded autonomic data provided converging measures of the concomitants of disordered information processing. PD patients ( n = 50) showed increased N1 amplitude to frequent non-target tones and reduced P3 amplitude to infrequent targets, compared to matched controls ( n = 98). There were no between-group differences for N1 targets, N2 or P2. Patients additionally showed increased heart rate, fewer spontaneous skin conductance responses (trend) to significant stimuli, and reduced P3 latency compared to controls, although the latter result was accounted for by patients who frequently experienced depersonalization and/or derealisation during panic. Patients showed several disturbances of attentive information processing in a simple auditory discrimination task: Increased N1 to repeated stimuli suggests impaired stimulus filtering, whereas reduced P3 amplitude and latency represent the under-allocation of neural resources for infrequent, goal-relevant stimuli, and their increased speed of processing, respectively. These disturbances likely contribute to patients' aversive outcomes in stimulus-rich environments.

Perceptual learning as a tool for boosting working memory among individuals with reading and learning disability

The majority of individuals with dyslexia and additional learning difficulties (D-LDs) also perform poorly on many simple auditory discrimination tasks. We now trained a group of D-LD teenagers on a series of auditory tasks and assessed their pattern of auditory improvement as well as their generalization to reading related tasks. We found that the performance of most D-LD participants quickly improved and reached the level of the general age matched population. Moreover, their pattern of learning specificity (e.g. no transfer from frequency to duration discriminations) was also similar to that previously observed in the general population. When assessed with a battery of verbal tasks that they initially performed poorly, a pattern of specific transfer was observed. Performance on verbal memory tasks improved to peer level, whereas performance on reading and non-verbal cognitive tasks did not. These findings suggest that D-LDs’ mechanisms of long-term learning are adequate. Moreover, perceptual learning can be used as a tool for improving general working memory skills, whose underlying mechanisms seem to be shared by simple tones and complex speech sounds.

Auditory event related potentials in patients with epilepsy on sodium valproate monotherapy.

The effects of antiepileptic drugs on event related potentials (ERPs) have been studied, but with contradictory results. In this study we examine the effect of sodium valproate (VPA) on ERPs in patients with epilepsy. Auditory event related potentials were recorded in 40 patients with idiopathic generalized epilepsy, 20 on monotherapy with sodium valproate (VPA), 20 on monotherapy with carbamazepine and 20 age and sex matched controls. All subjects performed a simple auditory discrimination task in which a target tone was presented on 20% of the trials. Mean P3 latency of the VPA group was significantly prolonged but not in carbamazepine group and healthy controls. We conclude that VPA monotherapy has an effect on P300 latency in patients with epilepsy. This difference might be attributed to effects of treatment with VPA and may clarify in the future the mechanism of P300.

Aging and the interaction of sensory cortical function and structure

Even the healthiest older adults experience changes in cognitive and sensory function. Studies show that older adults have reduced neural responses to sensory information. However, it is well known that sensory systems do not act in isolation but function cooperatively to either enhance or suppress neural responses to individual environmental stimuli. Very little research has been dedicated to understanding how aging affects the interactions between sensory systems, especially cross-modal deactivations or the ability of one sensory system (e.g., audition) to suppress the neural responses in another sensory system cortex (e.g., vision). Such cross-modal interactions have been implicated in attentional shifts between sensory modalities and could account for increased distractibility in older adults. To assess age-related changes in cross-modal deactivations, functional MRI studies were performed in 61 adults between 18 and 80 years old during simple auditory and visual discrimination tasks. Results within visual cortex confirmed previous findings of decreased responses to visual stimuli for older adults. Age-related changes in the visual cortical response to auditory stimuli were, however, much more complex and suggested an alteration with age in the functional interactions between the senses. Ventral visual cortical regions exhibited cross-modal deactivations in younger but not older adults, whereas more dorsal aspects of visual cortex were suppressed in older but not younger adults. These differences in deactivation also remained after adjusting for age-related reductions in brain volume of sensory cortex. Thus, functional differences in cortical activity between older and younger adults cannot solely be accounted for by differences in gray matter volume.

Poor Frequency Discrimination Probes Dyslexics with Particularly Impaired Working Memory

Substantial difficulties in performing simple auditory discriminations were previously found in some individuals with a specific reading disability but not in others. This high variability in psychoacoustic performance raises the question of whether this difficulty is related to the reading deficit. Addressing this question, we compared adult dyslexics with and without difficulty in simple auditory discriminations, using 2-tone frequency discrimination as our probe. The distribution of their frequency discrimination scores was bimodal. On this basis, we divided our participants into subgroups having either poor or adequate psychoacoustic performance. Only dyslexics with poor psychoacoustic scores had significantly impaired verbal working memory compared to their matched controls. Furthermore, and only in this subgroup, working memory scores were correlated with both cognitive abilities and reading-related tasks. Consistent with the hypothesis that in this subgroup poor working memory impedes performance in a broad range of academically related tasks, we found that the majority of dyslexics in this subgroup had more extensive academic difficulties and consequently needed special support in schools. We propose that dyslexics with poor psychoacoustic abilities form a distinct subtype of dyslexia in which the core deficit is not specific to phonological components. For these individuals, poor verbal working memory may be the main impediment to success in academic environments.

Generalization of cross-modal stimulus equivalence classes: operant processes as components in human category formation.

This study employed a stimulus-class rating procedure to explore whether stimulus equivalence and stimulus generalization can combine to promote the formation of open-ended categories incorporating cross-modal stimuli. A pretest of simple auditory discrimination indicated that subjects (college students) could discriminate among a range of tones used in the main study. Before beginning the main study, 10 subjects learned to use a rating procedure for categorizing sets of stimuli as class consistent or class inconsistent. After completing conditional discrimination training with new stimuli (shapes and tones), the subjects demonstrated the formation of cross-modal equivalence classes. Subsequently, the class-inclusion rating procedure was reinstituted, this time with cross-modal sets of stimuli drawn from the equivalence classes. On some occasions, the tones of the equivalence classes were replaced by novel tones. The probability that these novel sets would be rated as class consistent was generally a function of the auditory distance between the novel tone and the tone that was explicitly included in the equivalence class. These data extend prior work on generalization of equivalence classes, and support the role of operant processes in human category formation.

Handedness and P300 from Auditory Stimuli

The P3(00) event-related potential (ERP) was elicited in 20 left- and 20 right-handed normal young adult male subjects using a simple auditory stimulus discrimination task. P3 amplitude from the target stimuli was larger at anterior electrode sites for left- compared to right-handed subjects. P3 latency from the standard stimuli was shorter for left- compared to right-handers. The N1, P2, and N2 components generally demonstrated similar handedness effects. The relationship of ERP amplitude and handedness to anatomical variables and cognitive factors is discussed.

P300 topography of amplitude/latency correlations

The correlational association from 19 electrode sites between peak amplitude and latency for the P3(00) event-related brain potential (ERP) for n = 80 homogeneous subjects was assessed using a simple auditory discrimination task. The correlation strength varied systematically across scalp topography in different ways for the various ERP components. For the target stimuli, P3 amplitude and latency were negatively correlated and most tightly coupled over the frontal-central and right medial/lateral recording sites. In contrast, the N1 produced negative correlations that were strongest over the left and right central/lateral locations; P2 demonstrated a positive correlation that was strongest frontally and centrally; N2 demonstrated a positive correlations that was strongest over the central and parietal sites. ERPs from the standard stimuli produced generally similar patterns for the P3 and P2 components, with only weak or no reliable effects observed for the N1 and N2 potentials. Taken together, the findings suggest that analysis of amplitude/latency correlational relationships can provide information about ERP component generation. Theoretical implications are discussed.

Hippocampal and neocortical cell assemblies encode memory processes for different types of stimuli in the rat

The objective of this study was to determine whether each of several different memory processes is encoded exclusively by specific single neurons (single-neuron coding) or by overlapped groups of neurons (population coding by cell assembly). Single neuronal activity was recorded from the rat hippocampal formation (CA1, CA3, dentate gyrus) and temporal cortex during the performance of simple auditory, simple visual, and configural auditory-visual discrimination tasks. All the tasks employed the identical apparatus and time parameters and differed only in the type of stimuli to be processed for correct performance. Single neurons showing significantly differential activity among the discriminative stimuli in each task were judged to be task-related and involved in the memory process of the task. Of the total number of neurons recorded from the hippocampal formation and temporal cortex, 21-26% of the neurons showed task-related activity in only one task, in two tasks, or in all three tasks. This result indicates some overlapping among the neurons involved in each of teh different memory processes. A cross-correlation analysis tested activity correlations among the neurons recorded simultaneously. Most pairs of the hippocampal neurons related to the same tasks (same memory processes) showed correlations during performance of the related tasks. This result showing coactivation of the same types of task-related neurons, together with the result showing the overlapping of task-related neurons, supports the concept of population coding by cell assemblies specifically in the hippocampal formation during memory processing.

Hemispheric differences for P300 amplitude from an auditory oddball task

The P3(00) event-related potential (ERP) was elicited in 80 normal, right-handed male subjects using a simple auditory stimulus discrimination task, with electroencephalographic (EEG) activity recorded at 19 electrodes. P300 amplitude was larger over the right compared to left hemisphere electrode sites primarily at anterior-medial locations (F3/4, C3/4) for both target and standard stimuli. The N100, P200, and N200 components also demonstrated several similar, albeit less robust, hemispheric asymmetries. No hemispheric effects for P300 latency were observed, with few consistent latency findings for any of the other components obtained. The results suggest that the discrimination process underlying P300 generation may originate with right frontal activation.

P300 from an auditory oddball task: inter-laboratory consistency

Event-related potentials (ERPs) were recorded from normal subjects for the purpose of evaluating measurement consistency among six laboratories located in different cities within the United States. At each laboratory location 15 male subjects were tested using a simple auditory stimulus discrimination task and identical electrophysiological equipment and recording methods. Assessment of the N1, P2, N2, and P3(00) potentials from both the target and standard stimuli resulted in no reliable differences among laboratories for component amplitudes, latencies, and scalp distributions. Quantitative evaluation of overall waveform and specific component morphology yielded good to excellent agreement across laboratories. The findings suggest that large-scale inter-laboratory human electrophysiological studies are feasible and may prove of value when using ERPs to evaluate cognitive function in humans.

Spatio-temporal stages in face and word processing. 2. Depth-recorded potentials in the human frontal and Rolandic cortices

Evoked potentials (EPs) were recorded directly from 650 frontal and peri-Rolandic sites in 26 subjects during face and/or word recognition, as well as during control tasks (simple auditory and visual discrimination). Electrodes were implanted in order to localize epileptogenic foci resistant to medication, and thus direct their surgical removal. While awaiting spontaneous seizure onset, the patients gave informed consent to perform cognitive tasks during intracerebral EEG recording. The earliest potentials appeared to be related to sensory stimulation, were prominent in lateral prefrontal cortex, and occurred at peak latencies of about 150 and 190 ms. A small triphasic complex beginning slightly later (peak latencies about 200–285–350 ms) appeared to correspond to the scalp N2-P3a-slow wave, associated with non-specific orienting. Multiple components peaking from 280 to 900 ms, and apparently specific to words were occassionally recorded in the left inferior frontal g, pars triangularis (Broca's area). Components peaking at about 430 and 600 ms were recorded in all parts of the prefrontal cortex, but were largest (up to 180 μV) and frequently polarity-inverted in the ventro-lateral prefrontal cortex. These components appeared to represent the N4-P3b, which have been associated with contextual integration and cognitive closure. Finally, a late negativity (650–900 ms) was recorded in precentral and premotor cortices, probably corresponding to a peri-movement readiness potential. In summary, EP components related to early sensory processing were most prominent in lateral prefrontal, to orienting in medial limbic, to word-specific processing in Broca's area, to cognitive integration in ventro-lateral prefrontal, and to response organization in premotor cortices. Thus, multiple frontal areas are involved in multiple stages of face and word processing, in a highly parallel but nonetheless differentiated manner.

Spatio-temporal stages in face and word processing. 1. Depth recorded potentials in the human occipital and parietal lobes

Evoked potentials (EPs) were used to help identify the timing, location, and intensity of the information-processing stages applied to faces and words in humans. EP generators were localized using intracranial recordings in 33 patients with depth electrodes implanted in order to direct surgical treatment of drug-resistant epilepsy. While awaiting spontaneous seizure onset, the patients gave their fully informed consent to perform cognitive tasks. Depth recordings were obtained from 1198 sites in the occipital, temporal and parietal cortices, and in the limbic system (amygdala, hippocampal formation and posterior cingulate gyrus). Twenty-three patients received a declarative memory recognition task in which faces of previously unfamiliar young adults without verbalizable distinguishing features were exposed for 300 ms every 3 s; 25 patients received an analogous task using words. For component identification, some patients also received simple auditory (21 patients) or visual (12 patients) discrimination tasks. Eight successive EP stages preceding the behavioral response (at about 600 ms) could be distinguished by latency, and each of 14 anatomical structures was found to participate in 2-8 of these stages. The earliest response, an N75-P105, focal in the most medial and posterior of the leads implanted in the occipital lobe (lingual g), was probably generated in visual cortical areas 17 and 18. These components were not visible in response to words, presumably because words were presented foveally. A focal evoked alpha rhythm to both words and faces was also noted in the lingual g. This was followed by an N130-P180-N240 focal and polarity-inverting in the basal occipitotemporal cortex (fusiform g, probably areas 19 and 37). In most cases, the P180 was evoked only by faces, and not by words, letters or symbols. Although largest in the fusiform g this sequence of potentials (especially the N240) was also observed in the supramarginal g, posterior superior and middle temporal g, posterior cingulate g, and posterior hippocampal formation. The N130, but not later components of this complex, was observed in the anterior hippocampus and amygdala. Faces only also evoked longer-latency potentials up to 600 ms in the right fusiform g. Words only evoked a series of potentials beginning at 190 ms and extending to 600 ms in the fusiform g and near the angular g (especially left). Both words and faces evoked a N150-P200-PN260 in the lingual g, and posterior inferior and middle temporal g.(ABSTRACT TRUNCATED AT 400 WORDS)